Brittle fingernails are a common condition, occurring in about 20 % of people; more women than men develop brittle nails.
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Brittle nails usually break or peel off in horizontal layers, starting at the nail's free end. The term
brittle nails
can also refer to a condition in which lengthwise splits appear in the nail. In either case, the nail's structure is faulty.

Brittleness in the nail may be caused by trauma, such as repeated wetting and drying, repeated exposure to detergents and water, and excessive exposure to harsh solvents, such as those found in nail polish remover.
2,3
If your nails are regularly exposed to such stresses, it may be worth trying protective gloves when washing dishes and doing other chores. In the case of nail polish remover, gentler, less toxic brands are available. Check with retailers of natural cosmetic products.

Because of all these possibilities, it is important to rule out a serious underlying problem before trying nutritional or herbal treatments for brittle nails. If a medical cause for this condition is not found, it may be worth considering some of the approaches described below.

Principal Proposed Natural Treatments

Although no herb or supplement has been proven effective for brittle nails, there is some evidence that the B vitamin biotin might help.

Animal studies suggest that biotin supplementation can be helpful for deformed hooves in horses and pigs.
8-12
Since animal hooves are made of keratin, the same substance from which human nails are made, these findings have encouraged researchers to study the effects of biotin on brittle nails in humans.

Preliminary evidence from a small
controlled study
suggests that biotin may increase the thickness of brittle nails, reduce their tendency to split, and improve their microscopic structure.
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To arrive at their results, the researchers used a scanning electron microscope to examine the effects of biotin in 8 women with brittle nails who were given 2.5 mg of biotin daily over 6- to 9-month periods. (An additional 24 individuals were also studied; 10 served as controls, and the other 14 were examined in a way that makes the interpretation of their results questionable.) Because all nail clippings were examined without the researchers being aware of whose clippings they were looking at, these results have some validity. However, the study was too small to allow definitive conclusions.

Two small
open studies
also reported benefits with biotin supplementation.
14,15
However, because there was no control group in either study, the results can't be taken as reliable.

For more information, including dosage and safety issues, see the full
Biotin
article.

Other Proposed Natural Treatments

The mineral
silicon
has been widely marketed for decades as a treatment for brittle nails, brittle hair, and aging skin. However, the first potentially meaningful clinical trial was not reported until 2004. In this double-blind, placebo-controlled study of 50 women, use of 10 mg daily of silicon (as orthosilicic acid) for 20 weeks did appear to improve the condition of their nails.
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However, this study, performed by the manufacturer of a silicon product, leaves much to be desired in design and reporting.

The herb
horsetail(Equisetum arvense)
, naturally high in silicon, is also sometimes mentioned as a treatment for brittle nails A number of other nutritional therapies have been tried as well, including
calcium
, cysteine, gelatin-containing preparations,
iron
,
vitamin A
, and
zinc
. However, as of yet, there is no real evidence that any of these treatments are effective.
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